The present invention is concerned with a rapidly dissolving additive for molten metal, a process for the preparation of said additive and its use for the introduction of alloying elements into metals.
In the production of metal alloys, in practice the alloying elements are usually added in solid form to a molten metal bath. Thus, for example, aluminium is alloyed with magnesium in order to achieve improved strengths, with silicon in order to improve the castability and the strength and with manganese and chromium in order to increase the strength and corrosion resistance. Furthermore, a whole series of further alloying elements are known for the purpose of influencing alloying properties. Under current general practice alloying elements, in particular the alloying metal, which has a higher melting point in comparison with the base metal, is added in the form of a pre-alloy in order to achieve a rapid dissolving. The disadvantage of this pre-alloying is the limited content of alloying metal. Thus, for example the standard prealloys for aluminium alloying contain, besides aluminium, only a maximum of 20% of silicon, up to 20% of chromium or up to 50% of manganese. Thus, up to 4 times the amount of aluminium must be added to the alloying element; this results in higher transport costs, storage costs, energy consumption and the like. In order at least partly to avoid these disadvantages, it is known from U.S. Pat. No. 3,592,637 to use mixtures of aluminium or silicon powder with powders of alloying metals or alloying metal alloys in briquet form. Thus, for example, alloying briquets with 25% aluminium and 75% of the metals chromium, manganese and iron are commercially available. The disadvantages of such alloying agent are the proportion of alloying element being limited to 75% and the low speed of dissolving. British Patent Specification No. 2,112,020 also describes similar mixtures in which a part of the aluminium is replaced by chloride or fluoride salts. Commercially available tablets containing chromium, manganese and iron also have only a limited speed of dissolving.
Therefore, it is an object of the present invention to provide an additive for metal melts which does not display the mentioned disadvantages of the prior art but which, also in the case of higher concentrations of alloying metal, makes possible a complete and rapid dissolving in a molten base metal.